Brake arrangement for reversible hydraulic engines

ABSTRACT

In a hydraulic system for operating a reversible hydraulic engine there is provided a directional valve by which an idling circuit for said engine may be established through inlet and outlet conduits thereof. Each of said conduits includes a throttle valve and a check valve connected in parallel to each throttle valve. The throttling action of such throttle valves is optionally controllable by the operator in order to provide a controlled braking of the hydraulic engine.

United States Patent Sarnik et al.

1 Sept. 12, 1972 [54] BRAKE ARRANGEMENT FOR REVERSIBLE HYDRAULIC ENGINES [72] Inventors: Stanislaw Sarnik, Malmo; Mans Olof Olofsson, Asmundtorr, both of Sweden [73] Assignee: AB Kockum Landsverk,

skrona, Sweden 122] Filed: May 10,1971

[21] Appl. No.: 141,638

Land- [52] US. Cl. ..60/53 R, 91/404, 91/461 [51] Int. Cl ..Fl6d 31/06 [58] Field of Search...60/53 R, 53 WW; 91/404, 405,

[56] References Cited UNITED STATES PATENTS 2,789,542 4/1957 Vander Kaay ..60/53 R X 'pgi aeaea 1 i l i l 3,125,324 3/1964 Vivier ..60/53 R X 3,543,508 12/1970 Schwab ..60/53 R X 3,601,235 8/1971 Huf .60/53 WW X Primary Examiner-Edgar W. Geoghegan Attorney.lones and Lockwood [57] ABSTRACT ln a hydraulic system for operating a reversible hydraulic engine there is provided a directional valve by which an idling circuit for said engine may be established through inlet and outlet conduits thereof. Each of said conduits includes a throttle valve and a check valve connected in parallel to each throttle valve. The throttling action of such throttle valves is optionally controllable by the operator in order to provide a controlled braking of the hydraulic engine.

8 Claims, 3 Drawing Figures BRAKE ARRANGEMENT FOR REVERSIBLE HYDRAULIC ENGINES The invention relates to reversible hydraulic engines connected with a load of great inertia, and one object of the invention is to facilitate a more gentle and accurate braking of such engines than that achieved by using prior art brake arrangements.

Engines of the type referred to may be used for instance as drive engines in cranes and excavators in order to effect the swinging movement of the machine. Usually, the braking is achieved either by reversing the hydraulic engine, the directional valve of the reversible hydraulic engine being switched over to a rotational direction of the engine, opposite to that corresponding to the actual swinging movement such that the engine provides a braking force in the opposite direction, or by engaging a brake, usually a disk brake, mounted on the output shaft of the hydraulic engine. None of these brake arrangements is satisfactory. When reversing the hydraulic engine for braking the time of response i.e., the period between the time for switching over the directional valve and the beginning of the braking action is remarkably short and practically equals zero. Therefore, when braking it is difficult to predict the position in which the braked member will stop. By this rapid braking action the hydraulic system as well as the member driven by the hydraulic engine and elements connected therewith are subject to excessive strains. Since the pump of the hydraulic system provided for operating the hydraulic engine is used also for braking the engine the capacity of the pump cannot be utilized for operating other hydraulic members during braking. However, this may be desirable due to the fact that other movements often are initiated or performed during the swinging movement for instance in cranes or excavators. Thus, the pump must have a large capacity or must be supplemented by auxiliary pumps in order to allow other movements to be initiated or performed during the braking action achieved by reversing the engine, or it will be necessary to give up the advantage of performing other operations during the swinging movement. Both alternatives are inherently connected with substantial drawbacks. Also in case a brake is mounted on the output shaft of the hydraulic engine the time of response generally will be short and excessive strains will occur in the hydraulic system and the mechanical elements. Furthermore, such a brake involves a substantial additional investment.

In order to overcome the drawbacks mentioned above by modifying the hydraulic system and to provide at relatively low additional costs an arrangement facilitating a gentle and accurate braking of a reversible hydraulic engine connected with a load of great inertia and provided with inlet and outlet conduits for hydraulic fluid and a main control valve connected with said conduits to control the flow of hydraulic fluid for operating the engine in anyone of two directions and for allowing idling of the engine by short-circuiting of the conduits there is provided according to the invention a brake arrangement for such engines characterized in that in each of said conduits there is provided a throttle valve which is operable for controlling throttling action in the short-circuit by means of a common operating member to be optionally actuated by the operator, and a check valve connected in parallel with said throttle valve and allowing flow of hydraulic fluid to said engine.

In order to explain the invention as far as the construction and operation thereof is concerned and to illustrate the advantages achieved by the invention an embodiment thereof now will be described in greater detail with reference to the accompanying drawings wherein FIG. 1 is a diagram of a hydraulic system including a reversible hydraulic engine, in accordance with the invention;

FIG. 2 is a vertical sectional view of a valve unit included in the hydraulic system according to the invention; and

FIG. 3 is an enlarged sectional view of the valve unit according to FIG. 2.

A reversible hydraulic engine 10 which is connected with a mass of great inertia such as a large swinging mass of the type provided in cranes and excavators, has conduits 11V and llI-I for the supply and return of hydraulic fluid such as oil to and from the engine, respectively. Each of these conduits is connected by a valve unit 12V and 12H, respectively, to be described in detail later, with a directional valve 13 provided as the main control valve of the hydraulic system and with a conduit 14 communicating with an oil sump 15. A motor-driven pump 16 is connected to oil sump 15 by a suction conduit 17 through a filter 18 the pressure conduit 19 of said pump being connected with a conduit 20 communicating with oil sump 15 through a conventional overflow valve 21, with directional valve 13 through a check valve 22 allowing fluid flow in the supply direction only, and finally directly with directional valve 13. In conduit 14 there is provided a check valve 23 allowing fluid flow to oil sump 15 at a predetermined pressure in conduit 14 only, and a filter 24.

Directional valve 13 which may be constructed as a hydraulically operated valve has a central or neutral position shown in FIG. 1. In this position conduits 1 1V and 11H are interconnected through a central valve section 13N the pressure side of pump 16 being connected with oil sump 15 through conduit 19 and return conduit 14. Oil supplied by pump 16 thus will be returned to oil sump 15 engine 10 being able to operate in a closed idling circuit by pumping oil through conduits 11V and 11H via valve section 13N. If directional valve 13 is switched over to a right hand position section 13V thereof will be included into the hydraulic system which means that conduit 11V will be connected with pressure conduit 19 of pump 16, conduit 11H being connected with return conduit 14 through valve section 13V. In this case conduit 11V is the supply conduit of engine 10 and conduit llI-I is the return conduit thereof. However, if valve 13 is switched over to a left hand position valve section 13H thereof will be included in the hydraulic system which means that conduit 11H will be connected with pressure conduit 19 of pump 16 and conduit 11V will be connected with return conduit 14, conduit 11H thus being the supply conduit of engine 10 and conduit 11V the return conduit thereof. In the left hand position as well as in the right hand position of directional valve 13 the connection between conduit 19 and return conduit 14 is interrupted and so is the direct interconnection between conduits 11V and HR. The hydraulic system thus described is substantially of a conventional type;-the novel feature according to the invention is that in conduits 11V and 11H there are provided valve units 12V and 12H of a special type.

Valve units 12V and 12H are identical and the following description of valve unit 12V therefore applies also to valve unit 12H wherein the several details are provided with the suffix H instead of V.

Valve unit 12V comprises a throttle valve 25V, a check valve 26V connected in parallel thereto which allows oil to pass by the throttle valve in direction to the hydraulic engine 10, and an interconnecting conduit 27V connected with conduit 11V on the outlet side of throttle valve 25V and check valve 26V and interconnecting conduit 11V and return conduit 14. A check valve 28V allowing fluid flow from return conduit 14 to conduit 11V but not in the opposite direction is included in said interconnecting conduit 27V. Throttle valve 25V is biassed by a spring 29V to a throttling or closed position but from conduit 11V there is branched off on the outlet side of throttle valve 25V a conduit 30V for transmitting pressure on the outlet side of said throttle valve to an actuating means such as a plunger or the like which operates in a direction opposite to that of spring 29V such that throttle valve 25V is biassed to an open position by the pressure on the outlet side thereof. However, a corresponding actuating means for the actuation of throttle valve 25V in the biassing direction of spring 29V also is included in throttle valve 25V such actuating means being con nected with a conduit 31V communicating with a brake valve 32 which forms part of a hydraulic servo system. This brake valve may be operated by the operator for instance by means of a pedal 33 from a neutral position wherein there is established a communication through valve 32 between conduit 31V and the corresponding conduit 31H for valve unit 12H on one hand and a conduit 34 on the other hand said latter conduit being connected with an oil sump 36 through a filter 35. Suction conduit 38 of a servo pump 37 is connected through a filter 39 with oil sump 36 the pressure conduit 40 of said pump-being connected with oil sump 36 through filter 35 by a conventional overflow circuit 41 having an overflow valve 42, and with brake valve 32 through a conduit 43. By actuating brake valve 32 over pedal 33 it is possible for the operator to actuate throttle valves 25V and 25H against the pressure prevailing in conduit 30V and 30H, respectively, towards a more or less effective throttling. In the neutral position of brake valve 32 there is provided a connection between the hydraulic actuating means of throttle valves 25V and 25H, connected with conduits 31V and 31H, to enable oil received by these actuating means to return to oil sump 36 when the throttle valves are switched over to open position by the pressure in conduits 30V and 30H.

Conduits 44V and 44H, respectively, receiving and draining off leakage oil from throttle valves 25V and 25H are connected with sumps 45V and 451-1, respectively. In the practical embodiment of the hydraulic system described sumps 15, 36, and 45 are constituted by a common oil sump.

Before the operation of the hydraulic system thus described will be explained in greater detail a constructive embodiment of valve units 12V and 12H will be described with reference to the left hand valve unit 12V in FIG. 2. As will be understood the same description is applicable to the right hand valve unit 12H.

Each valve unit comprises a valve body having a bore 51 which is connected with the part of conduit 11V extending from the valve unit to hydraulic engine 10, and a bore 52 which is connected with the part of conduit 11V extending from the valve unit to directional valve 13. Between said two bores check valve 26V is arranged in an internal connection in valve body 10 formed by two mutually perpendicular bores 53 and 54. An extension of bore 54 forms conduit 27V, and to such extension is connected check valve 28V which may comprise a standard type check valve allowing fluid flow into bore 54 in valve body 50 and adapted to be connected with conduit 14. Throttle valve 25V is arranged in a bore 55 extending between bores 51 and 52, and this throttle valve is provided with connection means 56 for conduit 31V. Thus, it will be understood how the valve unit according to FIG. 2 is to be fitted into the hydraulic system disclosed in FIG. 1.

Valve 25V has a valve member 57 co-operating with a stationary seat 58 provided in bore 55 in valve body 50, to control the connection between bores 51 and 52 through bore 55. Valve member 57 is integral with a plunger 59 and is biassed by a pressure spring 60 corresponding to spring 29V shown in FIG. 1 and engaged between plunger 59 which is formed as a spring housing, and a support 61 fitted into bore 55, to bias valve member 57 towards seat 58. A passage 62 interconnects the opposite sides of plunger 59. In support 61 there is provided a bore 63, and the connection through this bore is controlled by means of a valve cone 64 which is biassed to a closed position by a pressure spring 65 engaged between said valve cone and a plunger 66 guided in a nipple 67 which is screwed into bore 55 and forms connection means 56 through which hydraulic pressure in conduit 31V is brought to act upon plunger 66 to increase the pressure exerted by spring 65 on valve cone 64. Support 61 and nipple 67 are formed as an integral unit and a transverse bore 68 is provided therein, conduit 44 being connected with said bore to drain off leakage oil passing through bore 63 past valve cone 64.

Check valve 26V comprises a plunger 70 formed integrally with a valve member 71 co-operating with a seat 72 formed at the mouth of bore 55. Valve member 71 is forced against this seat by a pressure spring 73 engaged between plunger 70 and a plug 74 screwed into the valve body.

It is assumed that directional valve 13 is switched over to the right hand position so that valve section 13V is included into the hydraulic system. Then, pump 16 delivers oil under pressure to conduit 11V which is the supply conduit of the hydraulic engine in this position of the directional valve; conduit lll-I being the return conduit of the engine is connected with oil sump 15 through valve section 13V. The connection between pressure conduit 19 and return conduit 14 of the pump is interrupted in valve section 13V. Oil supplied by pump 16 passes from conduit 19 through check valve 22 and valve section 13V to conduit 11V. Passing by throttle valve 25V which is maintained in a throttling or closed position by spring 29V the oil is supplied through check valve 26V to engine 10 through the remaining part of conduit 11V to drive the engine. It will be seen that the oil cannot pass through conduit 27V to conduit 14 since this is prevented by check valve 28V.

In return conduit 11H of engine the oil flows from the engine to valve unit 12H where the oil through conduit 30H actuates throttle valve 25H to an open position against the bias of spring 29. However, the oil cannot pass by check valves 26H and 28H. As will be clear from FIG. 2 the oil passes from the engine through conduit 11H to bore 51 and therefrom to bore 30H to be supplied through passage 62 behind plunger 59. Then, the oil will flow through passage 63 to bore 68 the oil being drained off from said bore to oil sump 45H through conduit 44H. Thereby, valve member 57 will be lifted from seat 58 against the bias of spring 60. From throttle valve 25H the oil will be returned to oil sump through valve section 13V, check valve 23 and filter 24.

Ifengine 10 is to be braked directional valve 13 is ac tuated and preferably is switched over initially to the neutral position thereof valve section 13N thereby being included into the hydraulic system. When pedal 33 is actuated the oil supplied by pump 37 through conduits 40 and 43 to valve 32 is brought to actuate throttle valves 25H and 25V through conduits 31H and 31V, respectively. This means that said valves will be operated to a throttling position. The throttling of valve 25V is of no significance to the operation of the system. However, the throttling of valve 25H effects braking of engine 10 since the engine has to operate against the back pressure provided by the throttling. The heavier depression of pedal 33 the heavier will be the throttling and thus the braking. Plunger 66 will be actuated by the pressure in conduit 31H in such a way that valve cone 64 will be more tightly engaged with the seat thereof in bore 63 of support 61. The heavier biassing of valve cone 64, the less oil will be able to pass this way to oil sump 45H which means that spring 60 willmaintain valve member 57 more tightly against the seat resulting in a greater throttling. If the pressure exerted on valve cone 64 is relieved by the return of pedal 33 the oil flow to bore 68 will increase to the extent that valve member 57 will be moved from the seat thereof thereby decreasing the throttling.

The brake arrangement according to the invention thus enables the operator to switch over the directional valve to anyone of the operating positions 13V and 13H, respectively, for operating engine 10 in the desired direction and to allow idling of the engine by moving the directional valve to the central or neutral position 13N the engine being braked more or less by the operators actuation of pedal 33. This means that the capacity of pump 16 may be utilized for operating other hydraulic drive members during braking. Thus, the invention eliminates the drawbacks referred to above in such a manner that the operator is completely free to have an effect on the braking.

At abrupt braking there may be built up in conduit 11V a great underpressure due to leakage in the engine and this may cause failing of pump 16 to maintain the supply of oil through valve 22 in the neutral position of directionalvalve 13, the pump supplying oil along the path providing the less resistance, i.e., through valve section 13N and return conduit 14 to sump 15. In order that oil shall nevertheless flow to the suction side of the engine, connection is provided through conduit 27V (27H) and check valve 28V (28H). Said latter valve is biassed to open after check valve 23 has opened if there is no underpressure in conduit 11V (11H). However, should such underpressure arise valve 28V will open.

Braking may be performed also with the directional valve in either of the end positions thereof. Then, pump 16 will operate against a back pressure which may reach such a value that overflow valve 21 will open.

In FIG. 3 there is disclosed a practical detail in the valve unit which is important for the function of the valve unit. On valve cone 64 there is arranged a loose washer 69 and this washer prevents oscillation of valve cone 64 such as may otherwise occur. This is due to the fact that oil passing through passage 63 will be deflected laterally thereby providing a hydrodynamic pressure force acting on valve cone 64, which is added to the static pressure acting on said cone. The washer may be replaced by a corresponding shape of valve cone 64.

What we claim is:

1. In a hydraulic system comprising a reversible hydraulic engine connected with a load of great inertia, inlet and outlet conduits for hydraulic fluid, connected with said engine, and a main control valve connected with said conduits to control the flow of hydraulic fluid to and from the engine, respectively, for operating the engine in anyone of two directions and for allowing idling of the engine by short-circuiting said conduits, a brake arrangement comprising a throttle valve in each of said conduits whichis operable for controlling throttling action in the short-circuit established by said main control valve, a common operating member to be optionally actuated by the operator for operating said throttle valves, and a check valve connected in parallel with each of said throttle valves and allowing flow of hydraulic fluid to said engine.

2. A brake arrangement as claimed in claim 1 wherein said throttle valve is biassed towards a throttling position and wherein there is provided first hydraulic actuating means for said throttle valve, said means being connected with said throttle valve on the side thereof which is connected with said engine, for actuating said throttle valve to an open position against the biassing action.

3. A brake arrangement as claimed in claim 2 wherein said throttle valve is provided with a second hydraulic actuating means for actuating said throttle valve towards the throttling position.

4. A brake arrangement is claimed in claim 3 wherein said throttle valve comprises a valve body, a throttle valve member, an actuating plunger displaceably guided in a bore formed by said valve body and operatively connected with said valve member, an interconnecting passage being provided in said: valve body between opposite sides of said plunger, a connection between one side of said plunger and one of said conduits, an outlet connected with the other side of said plunger, and a throttle member for controlling the flow through said outlet, said throttlev member being adjustable by said operating member.

5. A brake arrangement as claimed in claim 4 further comprising a spring biassing said throttle member towards the throttling position thereof the bias of said spring being controllable by said operating member.

6. A brake arrangement as claimed in claim, 5 wherein there is provided for said biassing spring an adjustable support member and means for actuating said support member by hydraulic pressure.

7. A brake arrangement as claimed in claim 6 wherein said throttle member is provided with a shoulder facing said interconnecting passage.

8. A brake arrangement as claimed in claim 1 further comprising check valve controlled supply means for 5 supplying hydraulic fluid to each of said conduits at an underpressure therein. 

1. In a hydraulic system comprising a reversible hydraulic engine connected with a load of great inertia, inlet and outlet conduits for hydraulic fluid, connected with said engine, and a main control valve connected with said conduits to control the flow of hydraulic fluid to and from the engine, respectively, for operating the engine in anyone of two directions and for allowing idling of the engine by short-circuiting said conduits, a brake arrangement comprising a throttle valve in each of said conduits which is operable for controlling throttling action in the shortcircuit established by said main control valve, a common operating member to be optionally actuated by the operator for operating said throttle valves, and a check valve connected in parallel with each of said throttle valves and allowing flow of hydraulic fluid to said Engine.
 2. A brake arrangement as claimed in claim 1 wherein said throttle valve is biassed towards a throttling position and wherein there is provided first hydraulic actuating means for said throttle valve, said means being connected with said throttle valve on the side thereof which is connected with said engine, for actuating said throttle valve to an open position against the biassing action.
 3. A brake arrangement as claimed in claim 2 wherein said throttle valve is provided with a second hydraulic actuating means for actuating said throttle valve towards the throttling position.
 4. A brake arrangement is claimed in claim 3 wherein said throttle valve comprises a valve body, a throttle valve member, an actuating plunger displaceably guided in a bore formed by said valve body and operatively connected with said valve member, an interconnecting passage being provided in said valve body between opposite sides of said plunger, a connection between one side of said plunger and one of said conduits, an outlet connected with the other side of said plunger, and a throttle member for controlling the flow through said outlet, said throttle member being adjustable by said operating member.
 5. A brake arrangement as claimed in claim 4 further comprising a spring biassing said throttle member towards the throttling position thereof the bias of said spring being controllable by said operating member.
 6. A brake arrangement as claimed in claim 5 wherein there is provided for said biassing spring an adjustable support member and means for actuating said support member by hydraulic pressure.
 7. A brake arrangement as claimed in claim 6 wherein said throttle member is provided with a shoulder facing said interconnecting passage.
 8. A brake arrangement as claimed in claim 1 further comprising check valve controlled supply means for supplying hydraulic fluid to each of said conduits at an underpressure therein. 